This invention pertains to circuit breakers providing thermal and magnetic trip in response to overload currents, such breakers being adapted for plug-in or bolt-in mounting on a distribution panelboard bus structure to protect branch circuits and connected apparatus emanating from the distribution panelboard. Particularly, this invention relates to an adapter which directly receives a standard circuit breaker of the aforementioned type and permits use of such breaker in an industrial control panel, motor control enclosure or other electrical control apparatus which does not have the bus structure of the distribution panelboard, but is hard-wired. More particularly, the invention relates to an adapter of the aforementioned type which itself has provisions for mounting on a panel or a DIN rail to function as a mounting base for a circuit breaker of the aforementioned type.
Certain motor control installations require thermal and magnetic protection for a motor. A motor circuit protector in combination with an overload relay will provide such protection at a sacrifice of panel surface area and apparatus cost. In many instances, circuit breakers of the type used for branch lighting and appliance circuits provide thermal and magnetic trip protection within the specifications of the particular motor. In addition, the circuit breaker can provide a disconnect function for the motor control circuit. Thus, panel builders and contractors often have need to place an individual or multi-pole circuit breaker in or on a panelboard or within a motor control enclosure.
Space is usually at a premium on or in panels or within electrical apparatus enclosures which greatly limits the location and type of mounting of the circuit breaker. DIN rails may be provided on or in panels and electrical apparatus enclosures for mounting motor control components, e.g. contactors, relays, overload relays, and it is convenient to be able to mount a circuit breaker to the same DIN rail structure. Manufacturers of circuit breakers, particularly European manufacturers, specially provide circuit breakers having a DIN rail mounting structure integrally molded in the case of the circuit breaker. The European style circuit breaker does not have plug-in or bolt-in connection with a distribution panelboard bus structure, but instead is provided with wiring connector terminals at opposite ends and may therefore be directly utilized in the motor control application. Domestic circuit breaker manufacturers also provide special circuit breakers for this motor control application which replace the plug-in or bolt-in type line side terminal with a wiring connector terminal. This substitution of terminal elements also requires different insulating case and cover members.
DIN rail mounting structures on circuit breakers or other molded case control apparatus comprise snap-on mounting and generally rely on a friction grip of the rail to prevent lateral sliding of the control apparatus along the rail. Spring biased elements for increasing the gripping force have been provided to improve the grip on the rail at increased cost of the apparatus.